This has alwasy been a favourite of mine - high-concept nonsense at its finest.

The core of a society spending their entire lives in their cars is incredibly on-the-nose, and I love it. RTD does what he does best, creating a world of memorable characters who each seem like they have full lives and personalities, with very little screen time. They really sell the absolutely absurd concept.

I don't think I've heard "The Old Rugged Cross" outside of this episode - Gospel isn't exactly my thing - but it's used well here, and I'm surprised to learn that it's an American song, and not something with British roots.

The "mood dealers" are an interesting idea, but somewhat underbaked. It seems like something they could have done more with, but here they're mainly a plot device to explain what happened to the overcity.

The idea of the Doctor bringing Martha back to New New New New New New New New New New New New New New New York is pretty solid, though I wish Martha didn't complain about it the way that she does. The unrequited crush angle continues to underwhelm, even though it's handled better in this episode than elsewhere. It's helped along by the fact that we can see the Doctor fighting with himself, slowly opening himself up to her against his own better judgement.

It's also nice to see the Face of Boe one last time - I've always felt that the character is diminished by the Captain Jack connection, and treat him as a separate character.

Oh, and Sally Calypso deserves her own spinoff based on her name alone.